The present invention relates generally to a system and method for spray painting pavement lines, and more particularly to and improved spray system and method for spray painting pavement lines with a plural component spray.
Plural component road marking systems consist of a resin or resinous material as being one component and a catalyst, (reactorxe2x80x94hardener) being the other component. To complete the system a third component, the reflective agent, which may also be made up of one or more components, is added, usually as a secondary operation to the spraying of the resin and catalyst. The two components, i.e., the resin and the catalyst must be brought together in a given ratio to facilitate the curing, hardening, of the material once applied. It is crucial that the mix of the two components be thorough, complete and accurate. Failure to achieve a thorough and proper mix, will result in various application failures, ranging from partial to full failures. An uncured line will not adhere to the road surface, leaving the roadway unmarked. In the interim moving traffic will track the uncured material indiscriminately across the road surface. The material will also be splashed onto auto finishes and glass areas causing considerable and expensive damage to autos. Improper curing because of improper application will also result in various failures. In addition to the hazards presented by a failed line, the correction is expensive and time consuming.
Slower drying materials require the use of traffic barriers to prevent moving traffic from tracking through slowly curing lines. These barriers may be a follow vehicle with warnings to traffic behind the striper to not pass or come between the striper and follow vehicle and the placement of traffic cones beside the new line to warn traffic not to come into the line. These traffic inhibitors are dangerous to both the motorist and workers and are the cause of many accidents resulting in death and serious injuries.
Newer developments in materials over the last few years have presented additional problems in the application and use of multiple component marking systems. To reduce some of the previous mentioned problems, primarily associated with slower cure times, faster curing materials such as those disclosed in U.S. Pat. No. 5,478,596 Richard S. Gurney have been developed. Some of the materials developed and certainly those to be developed in the future, set so fast, that the standard static mixing tube applicator system will no longer work. For clarification, a static mixing tube system relies on the resin and catalyst being physically mixed together by forcing the two materials together as they are flowed through a common tube with intermittent flow restrictors inside the tube, thereby causing the materials to xe2x80x9ctwistxe2x80x9d together. This system is archaic, and in fact insures that there will be at least parts of the application that will be improper. The two materials do not like each other and tend to resist mixing. In addition, this system requires frequent flushing with solvents to keep the system operational, (if not flushed, the mixed materials in the tube cake cure and block the tube). The solvents are not environmentally safe and by Federal and state laws are prohibited from being xe2x80x98dumpedxe2x80x99 on the ground. The solvents also degrade the road surface in the case of composite roads, by dissolving the tars holding the composite together, and causing the road to disintegrate. These solvents are poisonous and dangerous to humans and animals.
Many factors affect the final result, i.e., the materials meeting the road surface in the correct ratio and properly mixed to achieve cure as prescribed by the formula, slow enough to allow the injection of a reflective media prior to cure, fast enough to keep the reflective media from sinking to the bottom and being covered by the material; the definition of the line dimensionally and physically, being of proper width, thickness, uniformity, edge definition and square start and finish.
The considerations that must be given within a multi component spray system are factors governed by the characteristics of the material components. The component materials, rate of flow and the nature in which it flows as well as the various variables that enhance or inhibit the flow of the materials, including ambient heat, heat caused by flow, friction and resistance. Size of hose and pipe, valves, orifices, turns and radii all have an impact on the movement of the material components from a supply tank to the spray tip. The material components must arrive at the mix chamber and flow into the mix chamber in the exact ratio required to achieve the desired result. The two components do not have the same characteristics of flow at the same temperature and a line spray system operates in an environment that is unpredictable, that is outdoor weather has many variables that impact the temperature gain or loss of the material at various points in the system. A warm day with a high wind can cause heat loss that would be more severe than a cooler day with no wind.
It is imperative that when a line spray system is activated and material is sprayed from the gun, that all systems are in synchronous harmony to assure a perfect line at each start. With archaic systems, the only way this could be accomplished was to actually place a bucket under the gun and activate the gun until the system was producing materials in the correct proportion to cure. This was wasteful, time consuming and only a viable solution for a start-up, with no assurance that for temporary delays, such as a long wait at an intersection, that the gun did not freeze-up, or have an improper mix.
It is a primary object of the present invention to provide a novel and improved plural component striping spray system which effectively mixes the components by impingement prior to spraying.
Another object of the present invention is to provide a plural component striping spray system and method which mixes by impingement a resin and a catalyst under pressure in a spray gun mixing chamber prior to the spraying of the mixture through a spray nozzle. The spray gun and spray shutoff system for the spray gun is formed such that a minute amount of catalyst without resin exits the spray nozzle when spraying is initiated and terminated.
A further object of the present invention is to provide a plural component striping spray system and method wherein the components are brought to substantially the same viscosity before being mixed by impingement in a spray gun.
Yet another object of the present invention is to provide a plural component striping spray system and method wherein a spray gun for the system includes a restricted input orifice for each of the components and a recirculation system is provided to circulate each component through a restricted orifice remote from the spray gun and back to a supply tank when the spray gun is shut down. The remote restricted orifice for each component matches the restricted orifice for that component in the spray gun, and the pressure for the component is measured at the remote restricted orifice to determine component viscosity. The temperature of the components is then adjusted until the component viscosities are substantially equal.
A still further object of the present invention is to provide a plural component striping spray system which includes component storage tanks with internal temperature control mixing paddles.
These and other objects are achieved by providing a system wherein plural components are mixed by pumping them under pressure from heated supply systems and converting them into a fine spray within a spray gun where they mix by impingement within a spray gun mixing chamber before being blown out through a common spray tip orifice. The initiation and termination of spray from the spray tip is controlled by a shutoff needle, and the design of the mixing chamber, needle and spray tip are such that no mixed material is allowed to stay in the spray gun to cure and freeze up the gun.
The high pressure pumps used in the system are a stroking type pump, and therefore when the pumps change direction there is a fraction of time that the pump stops to reverse direction. At each change of direction a pulse is created in the material flow. The system alleviates this pulse problem by the use of accumulators that store up material at pressure and at the point of pump interruption provide a smooth material flow.
The flow of the materials is affected considerably by small changes in temperature, therefore the system incorporates the use of heat sources within the material tank that allows the material to flow through the heat source and provide a uniform temperature throughout the material. This system also facilitates the heating of material at a faster rate allowing for system operation at faster speeds and discharge rates.
The spray gun is heated to maintain temperature control up to exit of material. The material components are brought to the spray gun mixing chamber from opposing sides at high pressure and through a small input orifice intensifier. The chamber is made from a high wear resistance material to resist the erosive characteristics of the abrasive resins traveling through at high pressure and speed. Each input orifice is precision manufactured to maintain accuracy of mix. The orifices are matched to the flow and size of the tip to ensure proper back pressure ahead of the tip and force mixing to take place within the chamber assuring that mixed material exits the spray gun. The input orifices are also offset, with the orifice for catalyst being slightly lower than the resin orifice. This feature causes the catalyst to be the first input orifice to open and the last input orifice to be closed off by the needle action, which means that there never is resin only exiting from the tip which would, at the start or end of a sprayed line, leave an uncured spot or defect.
The system includes a recirculation system which becomes operative when the operation of the spray gun is terminated. This recirculation system is actually a spray simulator, duplicating the heat, pressures and flows that would exist in actual spraying, and the material from the recirculation system is recirculated back into the tank and storage system, blending with the material in the entire system. This prevents overheating of a small amount of material as well as assuring that the monitored material in this cycle is representative of the whole. The operator monitors the system in recirculation mode and when the indicators and gauges show that the system is in harmony, the operator is assured that when he opens the spray gun that the material mixture exiting is correct. Continuous monitoring while operating also tells the operator when something in the system has changed that would allow an improper mix material to be applied. The operator would have warning to shut the system down thereby preventing costly errors. This monitoring could be enhanced with audible and/or visual warning alarms.